/*
 * This file contains code from "C++ Primer, Fourth Edition", by Stanley B.
 * Lippman, Jose Lajoie, and Barbara E. Moo, and is covered under the
 * copyright and warranty notices given in that book:
 *
 * "Copyright (c) 2005 by Objectwrite, Inc., Jose Lajoie, and Barbara E. Moo."
 *
 *
 * "The authors and publisher have taken care in the preparation of this book,
 * but make no expressed or implied warranty of any kind and assume no
 * responsibility for errors or omissions. No liability is assumed for
 * incidental or consequential damages in connection with or arising out of the
 * use of the information or programs contained herein."
 *
 * Permission is granted for this code to be used for educational purposes in
 * association with the book, given proper citation if and when posted or
 * reproduced.Any commercial use of this code requires the explicit written
 * permission of the publisher, Addison-Wesley Professional, a division of
 * Pearson Education, Inc. Send your request for permission, stating clearly
 * what code you would like to use, and in what specific way, to the following
 * address:
 *
 *  Pearson Education, Inc.
 *  Rights and Contracts Department
 *  75 Arlington Street, Suite 300
 *  Boston, MA 02216
 *  Fax: (617) 848-7047
*/

#include <cstddef>
using std::size_t;
#include "screen5.h"

//private class for use by ScreenPtr only
class ScrPtr
{
	friend class ScreenPtr;
	Screen* sp;
	size_t use;
	ScrPtr(Screen* p): sp(p), use(1) { }
	~ScrPtr()
	{
		delete sp;
	}
};

class ScreenPtr
{
public:
	// no default constructor: ScreenPtrs must be bound to an object
	ScreenPtr(Screen* p): ptr(new ScrPtr(p)) { }

	// copy members and increment the use count
	ScreenPtr(const ScreenPtr& orig):
		ptr(orig.ptr)
	{
		++ptr->use;
	}
	ScreenPtr& operator=(const ScreenPtr&);

	// if use count goes to zero, delete the ScrPtr object
	~ScreenPtr()
	{
		if (--ptr->use == 0) delete ptr;
	}

	// constructor and copy control members as before
	Screen& operator*()
	{
		return *ptr->sp;
	}
	Screen* operator->()
	{
		return ptr->sp;
	}

	const Screen& operator*() const
	{
		return *ptr->sp;
	}
	const Screen* operator->() const
	{
		return ptr->sp;
	}
private:
	ScrPtr* ptr;        // points to use-counted ScrPtr class
};

ScreenPtr& ScreenPtr::operator=(const ScreenPtr& rhs)
{
	++rhs.ptr->use;     // increment use count on rhs first
	if (--ptr->use == 0)
		delete ptr;    // if use count goes to 0 on this object, delete it
	ptr = rhs.ptr;      // copy the ScrPtr object
	return *this;
}

